Contact assembly for electromagnetic relays



March 13, 1956 w. D. HAlLES 2,738,400

CONTACT ASSEMBLY FOR ELECTROMAGNETIC RELAYS Filed Dec. 31, 1952 2 Sheets-Sheet 1 Fig.1. 38 E 3 INSULATION II BII g5 INSULATION 18 BY Wm HIS ATTORNEY March 13, 1956 w. D. HAILES CONTACT ASSEMBLY FOR ELECTROMAGNETIC RELAYS 2 Sheets-Sheet 2 Filed Dec. 51, 1952 Flehl 2.

INVENTOR.

W. D. HAILES HIS ATTORNEY United States Patent 0 CONTACT ASSEMBLY FOR ELECTROMAGNETIC RELAYS William D. Hailes, Rochester, N. Y., assignor to General Railway Signal Company, Rochester, N. Y.

Application December 31, 1952, Serial No. 329,030 6 Claims. (Cl. 200-166) This invention relates to contact assemblies particularly adapted for use in electromagnetic relays, and more particularly pertains to contact assemblies of the multiple contact finger type where the movable contact fingers are linked together by a common pusher member which is in turn operated by the action of the relay armature.

In my prior Pat. No. 2,237,274, granted April 1, 1941, a method of forming multiple contact finger assemblies by molding such fingers into a Bakelite block was shown and described. Although this prior method of forming multiple contact assemblies has been extensively used commercially, there are certain problems involved which the present invention has overcome.

For example, when the contact finger assemblies are molded in Bakelite blocks, it is found that a large number of different combinations of assemblies are required to be kept in stock. This is due to the fact that the relays are used in different types of circuit organizations and the contact requirements for the relays vary widely.

It has also been found that the molding dies, although made as accurately as possible, permit a slight amount of the Bakelite powder to squeeze through or around the partitions of the mold and adjacent the contact fingers during the molding process. As a result, a slight lip or ridge of hard Bakelite will be present at ,thep'oints where themetal contact fingers extendfrom the molded block. Since these extending lips may interfere with the flexing action of the contact fingers during operation of the relays, or may tend to break off and fall into the relay housing during operation, it is obvious that these overhanging lips or ridges of waste Bakelite must be removed from the contact assemblies before they can be mounted in the relay structure for actual use. Not only has this process of cleaning and smoothing the Bakelite blocks been found to be expensive, but there is also the possibility that some vsmall portion ofhardened Bakelite material will be overlooked. This is particularly dangerous in connection with the manufacture of relays foruse in railway signalling systems, and the like, where the highest degree of safety isrequired. Obviously, a loosened or broken piece of Bakelite in arelay housing may cause considerable difficulty in the relay operation should it fall into some strategic location.

In view of theabove considerations, one. Obj ct of the present invention is to provide for the separate manufacture of molded Bakelite blocks and the contact fingers to be assembled in such blocks. The separate molding of the contact blocksprovides that therearenoextruding lips except perhaps where the Bakeliteipowder is poured into the mold. Such ridges or wasteBakelite can, of course, be readily removed. The assembly of the contact fingers in the molded blocks can .then be made in any desired combination when the relay is being assembled and its contact requirements are known, thus decreasing the number of different contact assemblies which mus-t be stocked during the manufacture of different relays of varied contact capacity. This manner of constructing multiple contact finger assemblies also permits the removal and replacement of damaged contact fihgerswithoutdiscardingthe. entire contact assembly as would be the case where the contactsare-permanently molded in the blocks.

A still further object of the present invention is to provide a contact finger structure which can be prefabricated before the assembly in the molded block, and which can be readily adjusted with respect to its cooperating contact fingers after it is assembled in the contact block without changing its initial spring tension. More particularly, the features herein disclosed which relate to the structure of the contacts themselves are disclosed and claimed in the copending application Ser. No. 416,373, filed March 15, 1954.

Generally speaking, and without making any attempt to define the exact nature of the invention, it is proposed that each contact supporting block be made by the usual molded Bakelite process with each block provided with a full quota of slightly tapered holes or recesses therein to receive the prefabricated contact fingers as desired for the particular combination being made. It is proposed that each contact finger be provided with a slightly tapered retaining unit which is constructed with a plurality of teeth or fingers for gripping the inside of the tapered hole in the Bakelite block in which it is to fit. It is also proposed that the insertion of these contact fingers into their respective holes in the Bakelite contact block be effected by suitable tools under predetermined conditions of pressure and the like so that the assembly of the fingers in their respective blocks can be effected rapidly and uniformly. In addition, it is proposed that the contact finger structure with their retaining units be so constructed that they can be removed if necessary for changes or replacements.

For a more detailed description of the parts and the method of ,their assembly, reference should be made to the following description and the accompanying drawings, in which:

Fig. 1 is a sectional view of a typical relay structure having a multiple contact finger assembly mounted thereon as constructed in accordance with the present invention;

Fig. 2 is an enlarged sectional view of a part of the multiple contact finger assembly showing one of the contact fingers in a position in readiness for insertion into the molded contact block;

Fig. 3 is a back view of one of the molded contact blocks showing the openings therein and a sectional view of the contact fingers as mounted in such openings;

Fig. 4 is an enlarged view of one of the openings in the molded contact block and with a contact finger and retainingunit mounted therein as shown in Fig. 3;

Fig. 5 is an enlarged perspective View of one of the contact retainer units;

Fig. 6 is an enlargedview similar to Fig. 4 and shows the manner in which a tool may be employed to remove the contact retainer uni-t;

Fig. 7 is a top view of a contact finger as it has been prefabricated for assembly in the molded contact block;

Fig. 8 is a side view ofthe contact finger shown in Fig. 7;

Fig. 9 is an exploded view of the contact finger structureshowninFigsh7 and 8 to illustrate the relationship between the different parts prior to assembly;

Fig. 10 is a detailed top view of a single contact spring as shown in the contact finger of Figs. 7 and 8;

.Fig. 11 illustrates a movable contact finger and the associated pusher member which is actuated by the armature for cooperation with the various front and back contact fingers as illustrated in Figs. 1 and 2; and

Fig. 12 shows a top view of an idler or guide finger used to hold the pusher member in place.

Referring to Fig. l, a plug-in type relay has been shown as having a contact assembly mounted thereon as constructed in' accordance with the present invention. This complete relay structure is shown as comprising in 3 general a back plate 11, an electromagnet structure 12, a coopera n" armature 13, a molded contact block and finger assembly 14 and a plugboard 15.

More specifically, the electromagnet structure 12 of the relay includes a coil or winding 16 on a suitable core having a pole face 9 which is adjacent to the armature 13. The armature 13 is L-shaped and pivotally supported on a top yoke 17 so that when the winding 16 is energized, the armature i3 is attracted which causes an extension arm 13 attached to the armature 13 to be raised. This extension arm 18 is of insulating material. The top yoke 17 is attached to the backplate Ill and forms a part of the magnetic structure. The extension arm 18 attached to the armature 13 lies between the top yoke 17 and the contact block and finger assembly 14, and is provided with a suitable backstop 28 which rests on the top of the yoke 17 when the armature is in its retracted or deenergized position.

The contact block and finger assembly 14 is fastened to the backplate 11 by means of a bolt 15 and a screw 29. The screw 2i passes through a hole in the molded block 21 and also a hole in the base or bacltplate 11 so as to engage a nut that is wedged against the base plate 11. The block 21 is provided with a recess for the reception of a biasing spring 26 so that the block 21 will be pressed against the head of the screw 2% and the turning of the screw 29 can cause the position of block 21 to be adjusted since the block 21 is provided with a rounded protrusion at its lower end which is caused to rest against the base plate ll by the bolt 19.

The molded contact block and finger assembly 14- constitutes a molded block 221 of suitable insulating material such as a plurality of similar recesses molded therein for receivin prefabricated contact fingers in different combinations. For the purposes of illustration, a front contact combination A is shown as comprising a fixed contact finger structure and a movable contact finger structure. A back contact combination B is similar except that the fixed contact finger structure is located beneath a movable contact finger structure. In addition, a contact combination C is shown which comprises a fixed front contact structure, a movable contact finger structure, and a fixed back contact finger structure. In addition, this fixed back contact finger structure for combination C is provided with an idler finger 27 since this back contact finger structure is at the bottom of the assembly. This idler finger 27 is acted upon by the armature extension 13 and serves to position the lower end of a common pusher bar 22 which in turn acts upon all of the movable contact finger structures when the armature is operated. The upper end of this common pusher bar 22 is held in position by the uppermost movable contact finger structure, as will be described later. This pusher bar 22 is, of course, made of suitable insulating material.

Although there is no front view of the relay, it should be understood that two or more of the molded block and contact finger assemblies 14 may be mounted side by side with their respective idler fingers 2! resting on the armature extension 18 so that all such assemblies are operated together. in this way, the relay may be made to have a substantial number of different contact combinations.

In the embodiment disclosed herein, the molded block 21 is provided with eight recesses for receiving contact finger structures orassemblies. Referring to the enlarged view of Fig. 2, it will be noted that each of these recesses or holes 39 for receiving contact finger assemblies has bevelled edges 31 at each end. This not only assists in placing the contact finger assemblies, but also increases the surface distance between the adjacent contact finger assemblies to give an added electrical isolation. The center portion of each of the recesses 35! is tapered throughout its entire length for the purpose of providing the draft required to withdraw the pins used in molding these holes. The front end 39a of each hole is approximately two thousandths of an inch larger than the back end of that hole 3%. The center portion of each hole is grooved as shown at 32 (see Fig. 3) for the purpose of allowing the entrance of the contact finger structure which has rivet heads protruding on one side. Since each of these contact finger structures may be inserted with either side up, recess 39 must be provided with a groove 32 on each side. This can be readily seen by the illustration of Fig. 3.

The front and back contact finger structures 24 and 25 are exactly the same in construction where they engage the block 21. The only differences are in their manner of mounting in the molded block 21 and the direction in which the terminal end is formed at the back of the relay. One of these contact finger structures has been shown in detail in Figs. 7 to 9 and enlarged to readily show its structural characteristics.

Since each such structure may be used in either a front or back contact combination A or B, entirely diderent reference characters are used in these detail figures. This contact finger structure (see Fig. 8) coinprises a contact spring 34, a stop member 35 and a retainer unit 36 all fastened together with rivets 37. The contact spring is preferably stamped from phosphor bronze and is bifurcated at its free end, each bifurcation of which is supplied with suitable contact points or tips 40. These may be made of silver, or other suitable contact material. Referring to Fig. 9, it can be seen that the contact spring 34 is stamped with a particular contour including the offsets 42a, 42b and 420. The offsets 42b and 42c also have slight indentations, one on each side of the center line of the spring 34 right at the point of the offset angle, and these indentations serve to reinforce or stifien the contact spring at that point. An indentation 42d is provided at the extreme right-hand end to form a sharp nib to serve as a contacting surface for the plug coupling connection as can be seen in Fig. 1.

The contact spring 34 in addition to being bifurcated is also slotted as can be seen in Fig. 10 to provide a passage space for the free movement of the insulated pusher bar 22. In addition, a rectangular shaped hole 41 is provided for receiving the outer end or hook 44 of the backstop or support member 35.

Referring to Fig. 9, it can be seen that this backstop or support member 35 is provided with an offset finger or backstop hook 44 which, as seen in Fig. 7, is sufliciently narrow as to freely fit into the hole 41 of the associated contact spring 34 for supporting such spring as seen Fig. 8. The support or backstop member 35 also has a pressed out detent or nib 43 extending downwardly as viewed in Figs. 8 and 9 so that when the contact finger structure is assembled, the contact spring 34 is supported between the hook 44 and the detent or nib 43 as best seen in Pig. 8. In this connection. it should be noted that the particular preformed contour of the contact spring 34 (see Fig. 9) is such that this spring 34 presses slightly against the detent 43 when the structure is assembled. This means that there is no intentional trapped pressure of the spring 34 against the hook 44. Also, the underpoint of detent 43 is located above the surface of the hook 44 a distance substantially equal to the thick.- ness of the spring 34. in this way, the spring 3 is held in a definite position located by the backstop member 35.

Each contact finger structure or assembly is provided with what may be termed a retainer unit 36 which is shown in perspective in Fig. 5 and which is shown in a side view in Figs. 8 and 9. This retainer unit 36 is preferably made from Phosphor bronze and is of a gen: eral U-shape with spread legs in cross section (see Fig. 4). It is formed with a fiat surface and two bent sides which extend outwardly at an appropriate angle. Each side is serrated so as to form sawteeth or projections 46. The edges of the projections or teeth are tapered so as to form points as at 47. These successive points along the sides of the retainer unit 36 are bent so as to provide an ve a tape in h ig fi e th oug ou the entir length which is;approximately a few thousandths (such as ten to fifteen thousandths) of an inch smaller at the end 36a than at-the end 36b, so that this taper in height of the points will insure that the last point to enter a hole will be properly stressed even though the other points may have enlarged the hole by cutting a small groove in the Bakelite of the block 21.

As above mentioned, the retainer unit 36, the spring finger 34 and the backstop or support member 35 are assembled and riveted by rivets 37. Referring to Fig. 4, the normal shape of the retainer unit 36 is shown in dotted line, but when the contact finger assembly is inserted into the recess in the molded block 21, the sawteeth 46 are bent upward and outward to assume the full line positions shown in Fig. 4. The degree of this deformation is suchas to bebeyond the elastic limit and yield point of all of the teeth on all fingers, so that the pressurejor holding the contact finger assemblies in position will be fixed and stabilized at the value established by the yield point of the retainer. This construction insures that each finger will be held by substantially the same forces acting against the top and bottom faces of the hole in which it is placed even though the finger dimensions and hole dimensions are slightly diiferent because of ditferences in manufacture that can not be overcome except at great cost. It also insures that the Bakelite block 21 will not be overstressed or even cracked by forcing an oversize finger assembly into an undersized hole as -might be possible with another type of finger design.

For example, a spring retainer unit having a yield point of fifty pounds has been found acceptable in a practical design.

lt might be mentioned in this connection that by the insertion of a relatively thin tool49 into the recess beneath the teeth 46 and from the rear of the block 21, the teeth can be bent still further beyond their yield point and then the contact finger assembly may be readily removed. This is'illustrated is shown inserted in one of contact finger assembly.

Each of the movable contact fingers 23 (see Figs. 1 and 1-1.) is made with an elongated slot similarly as shown in Fig. for the contact spring 34, except of course there is no bifurcation. The uppermost movable contact finger 23 has its slot divided by web 39 into two parts as shown inFig. 11. The other movable contact fingers '2'3'are'exactly the same as shown in Fig. 11 but without the web 39.

The web 39 of Fig. 11 provides a small rectangular hole for receiving the upper end of the pusher 22 when it is properly positioned, which hole causes the finger 23 to beengaged by the adjacent protrusion on the pusher '22. .It is noted that the larger of the two holes shown in Fig. 11 for the finger 23 is sufliciently large to freely eceive the pusher 22, as will be explained below.

Referringto Fig. 1, it will be noted that the movable contact finger 23 is in the second from the top recess of the block '21; and for this reason the pusher 22 has to have its upper section 38 (shown in dotted) removed sothat the proper protruding section of pusher 22 will engage-the movable contact finger. If the combination B were to be used in the upper'two spaces for the block 21 instead of the combination A, then the pusher .22 wouldbe of the regular length including the dotted portion 38.

A topviewof theidler finger 27'has been shown in Fig. 12 toindicate its shape and to show that the rectangular hole 50 is of justthe proper size to receive the lower end of the pusher 22 and-be engaged by the next adjacent protruding portion of the pusher.

When all of the contact finger structures are in position, the pusher bar 22 can then-be slipped through the slots inthe fixed and movable contactfingers fromthe the holes 30 beneath the in Fig. 6 Where the tool 49 top o t e sem let s emb y d down t u h larger slot of the upper movable contact spring and the lower end is inserted in the hole in the guide spring 27 which is then pushed downwardly until the upper end of the pusher bar 22 can be slipped into the smaller hole of the uppermost movable contact finger. When this is done the pusher bar moves forward to engage each of the movable contact fingers with its corresponding projection. It can thus be seen that the pusher bar 22 then pushes against each of the movable contact springs 23 when the armature 13 is actuated to cause its extension 18 to be moved upwardly.

In this connection,-the pusher bar 22 is provided with a projection at its lower end which engages the hole in the guide spring or idler 27 and there is an extension or protruding portion for each of the successive spaces of the contact block 21 so that a movable contact finger can be placed in any one of the several spaces of the contact block and be properly operated by the pusher bar 22. However, when the uppermost space is a front contact, then it is apparent that the uppermost section of the pusher bar must be removed, so that it will be of a length shown in Fig. 1 for properly being received in the hole of the movable contact finger 23 in the second space of the molded contact block 21.

In summary it may be said, that the purpose of the contact finger assembly is provided with a single piece type of stop member for the stationary or fixed contact fingers so as to reduce the initial cost and to reduce the time required to adjust the contact finger assemblies after they have been placed on a relay. It is well known that the contacts of a relay are usually adjusted to provide a predetermined gap between the movable and fixed contact points when they are open, and to provide a'predetermined contact pressure when they are closed. With the single plate type of stop construction described herein, the fixed contact spring is formed, as above described, to have a particular spring bias against the pressure nib or detent 43 of the stop plate. Thus, even though the stop member 35 is adjusted by bending to move the fixed contact spring to the proper position with respect to the movable contact so as to make and break at specied points in the travel of the movable contact, the contact spring 34 is firmly held in the new position and the proper tension is provided when the contacts are closed. This means that the contact springs 35 of the fixed contacts will follow the pressure nib 43 as it ,is moved up or down when the stop member is adjusted. Since the back stop hook extension 44 is also a part of the back stop member 35, it also will not change its position relative to the contact spring 34. Hence, the

contact position may be adjusted by a single operation in contrast to prior structures which employ two separate backstopjmembers, one on each side of the contact spring. It should be noted that when the backstop member is bent, suchbending takes place near the rivets 37 because the backstop member 35 is narrowed at 45 near the rivets 37 as seen in Fig. 7.

By designing the contact springs 24 and 25' (see Fig. l) in proper proportions, the contact pressure built up in the fixed contact springs as they are deflected by movable contact springs 23 pushing against them is determined by fixing the amount of contact compression and the amount ofrnovable contact travel. In this Way, the necessary contact pressure can be obtained without the cost and time involved in testing the pressure of each individual contact.

In this connection, it should be noted that each of the movable contact springs 23 is preformed so as to have enough pressure or spring bias to fully compress its back contact spring, and thus a relay can be quickly checked without the use of agauge by noting that each movable contact spring on the relay is following its pusher bar all the way down toits lower position when the armature 13 releases. Thus, built-in pressure for the movable contact springs must be within predetermined limits so that the relay Will not require excessive operating current. Thus, a test of the relay to determine its operating characteristics thus called for in accordance with its design, will indicate whether or not the pressure in its movable contact springs are within the proper limits. An excessive operating current will indicate an excessive down pressure of the movable contact springs, but this will not occur except in faulty manufacture or preforming of the movable contacts.

Therefore, it can be readily seen that this construction simplifies the adjustment of each fixed contact to a relatively simple bending operation of the whole fixed contact assembly up or down a small amount as may be required to properly locate that finger with respect to its associated movable contact finger to give the values required for that particular relay.

it is also to be understood that various modifications may be made to the structure within the scope of the present invention. For example, the fixed contact fingers can be made into a make-before-break type of contact by bending the pressure nib or detent 43 back into alignment with the backstop member and causing the conagainst the hook member 44. The stop member 35 can then be adjusted to make and break with its movable contact at any point in its operation.

Having thus described a molded contact block and finger assembly and a method of assembling the structure as one specific embodiment and illustration of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume; and, it is to be further understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice Without in any manner departing from the spirit or scope of the present invention.

What I claim is:

1. In a contact finger structure, a contact spring having one end bifurcated and having contact points on the biturcated portions and having a mounting structure at the other end comprising a retaining member with a spreadleg shape and protruding teeth at the ends of the legs, an insulated block with a recess of such width and depth as to receive said retaining member only providing said toothed legs are forced further apart to thereby produce a firm holding action against the inner surface of said recess when said retaining member is inserted end-wise into said recess.

2. In a contact finger assembly comprising, a molded insulating block. having a plurality of recesses, and a plurality of contact finger structures each comprising a contact spring, a relatively rigid backstop member and a retainer member all riveted together near one end of said contact spring, said retainer member having a plurality of t eth along each side and of a general spreadleg shape, and said contact finger structure at said one end being slightly deeper than the depth of its recess, whereby the insertion of each contact finger structure in its respective recess of said block causes the legs of its rctainer unit to be further spread and beyond the elastic limit and yield point of that member.

3. A contact finger structure for electromagnetic relays comprising a plurality of separately formed contact linger assemblies and a molded insulated block having a plurality of recesses for respectively receiving said contact finger assemblies, each of said contact finger assemblies comprising a contact spring, a single plate backstop memher and a retaining member, said backstop member and retaining member being riveted together to said contact spring at one end, said retaining member having a spread-leg shape with a series of teeth along each side of suificient length so that the insertion of each contact tact sprin" 3:; to have an intentional trapped pressure finger assembly in its respective recess causes the spreadlegs of that retainer unit to be moved beyond the yield point of the metal, whereby the holding pressure for each contact finger assembly is the same and within a predetcrmined range.

a. A contact assembly comprising, a molded insulating block having a rectangular shaped recess formed therein, a contact finger structure including a spring with a contact at one end and a retainer member at its other end, said retainer member being of a general shape to fit said recess and having two rows of teeth along the edges of one side to form a spread-leg shape, said teeth being sufficiently long to require their being spread further apart when said assembly is forced into said recess, whereby a firm holding action against the inner surfaces of recess is maintained by said retainer member and said contact finger is thereby held in a proper position.

5. A contact assembly comprising a molded insulated block having a recess included therein of generally rectangular shape, a contact finger formed by a spring with a contact at one end and a retaining member attached thereto at its other end, said retaining member being formed of a. spring type material with a predetermined yield point and of a shape generally rectangular with two rows of teeth one on each edge of one side to form an arch for insertion into said recess, said teeth being relatively long and spread at a slant to cause the further spreading of said teeth as said retainer member is inserted into said recess until the teeth are spread beyond the yield point of said material, whereby the holding pressure of said retainer member against the inner surfaces of said insulated block is of a predetermined value determine-cl by the resiliency of said retainer member when bent beyond its yield point.

6. A contact assembly comprising a molded insulating block having a plurality of spaced recesses in a row included therein, said recesses being generally rectangular in shape and slightly tapered toward the back of said block, a plurality of contact fingers each including a contact spring with a contact at one end and a retaining member attached thereto at its other end, said retaining memher being formed of a spring type material with a predetermined yield point and of a generally arched shape with two rows or": eeth arranged for insertion into one of said recesses until the teeth are spread beyond the yield point,

ertain of said contact fingers also including a single backstop member of relatively rigid material located substantially parallel to its said spring and also attached to its retaining member, said contact fingers being arranged and inserted in the recesses of said blocks in the desired combination with those contact fingers being movable with respect to said certain contact fingers having the backstop members, and an insulated operating member interconnecting the movable contact fingers and biased by them to a particular position, and a holding finger mounted at the bottom of said block for holding said operating member against the normal bias of said movable fingers.

References Cite. in the file of this patent UNITED STATES PATENTS 1,817,775 Sipe Aug. 4, 1931 1,971,726 Norwood Aug. 28, 1934 2,006,813 Norwood July 2, 1935 2,055,329 Benander Sept. 22, 1936 2,134,945 Howe Nov. 1, 1938 2,249,381 Gustafson July 15, 1941 2,258,122 Merkel Oct. 7, 1941 2,543,036 May Feb. 27, 1951 2,553,917 Hartman May 22, 1951 FOREIGN PATENTS 116,354 Sweden Oct. 22, 1946 585,445 Great Britain Feb. 6, 1947 608,960 Great Britain Sept. 23, 1948 991,737 France June 27, 1951 

